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pvc pipe laser in need of some serious help

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genoober

Wed Aug 31 2011, 10:07AM

Registered Member #4055 Joined: Tue Aug 16 2011, 06:56AM
Location:
Posts: 8

So I picked up this .25 inch by 4 in nd:yag rod... and I have about 30 disposable cameras.. I plan to place the nd yag inside of a pvc pipe with three sets of three nylon screws .25x20 I plan on cutting "windows" for the flashes from the disposable cameras and painting the inside of the pipe with reflective krylon.

Does this sound like it would work??? I plan on using a 12v 2amp power supply to charge the capacitors to 330v with a transformer. Hopefully with an efficiant design I can get around 20 pulses per second

I'm not a big electronics guy would anyone like to assist with the circuit design? And triggering system?

MArked One

Wed Aug 31 2011, 10:42AM

Registered Member #3688 Joined: Mon Feb 14 2011, 07:39PM
Location: Europe
Posts: 38

Greetings.

It would be good if you elaborated on your setup a little.
I assume that you have an optical resonator set up. What mirrors are you using?
I think a big problem would be achieving a fast enough (230 us) risetime for your lamps. You would be better off building a pumping system from scratch, with a flashlamp that's designed for optical pumping. (Ebay's lousy with them)

You should check out Sam's laser FAQ, particularly these chapters:

and

Did you invest in a pair of 1064nm glasses? If you catch a reflection in the eye, you'll probably have to live with a permanent smudge from the optical damage.
One more thing: If you do try to fire the laser with your current setup, do try to align it properly with a red pointer or HeNe, or you could damage your windows or rod.

I hope this helps.

Kind Regards,
Ivan Kozlov.

Dr. ISOTOP

Wed Aug 31 2011, 02:18PM

Registered Member #2919 Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652

I doubt it'll lase, but that's just the pessimistic side of me talking.
You'll also need an HR and an OC, and you need to make sure your rod was meant for pulsed operation. Is it an SSY-1 rod?
Come to think of it, you're probably better off getting an SSY-1, or at least parts of one, off Ebay.

Forty

Wed Aug 31 2011, 08:32PM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

it might be easier to just use a metal pipe and polish the inside.

Daedronus

Wed Aug 31 2011, 09:07PM

Registered Member #2329 Joined: Tue Sept 01 2009, 08:25AM
Location:
Posts: 370

there are suitable ceramic pump chambers for sale on ebay, at reasonable prices. (if it's there the option always use the best offer with something like 50 - 60% of the original price).

There is no substitute for a proper reflector/pump chamber.
What you plan to do will work, nd:yag is very forgiving, but it will be crappy.

I did experiments with aluminum foil closly wrapped around the nd:yag + flash lamp, and it work, but it was really crappy, maybe about 40% of what I got from a proper pump chamber.

You don't necessarily need the discharge time to be 240us, even 2-3 ms is fine, it's just that you get a different pulse shape.

MArked One

Thu Sept 01 2011, 10:15AM

Registered Member #3688 Joined: Mon Feb 14 2011, 07:39PM
Location: Europe
Posts: 38

Do you know the doping percentage of your rod?
Do you know where it came from?

genoober

Fri Sept 02 2011, 10:15AM

Registered Member #4055 Joined: Tue Aug 16 2011, 06:56AM
Location:
Posts: 8

No real setup yet. no optical cavity. nor even mirrors yet... I am still sourcing parts. One of my goals here is to build a 100% free laser. My experiance with lasers is a little lacking and I am safty paranoid so unless I can find free laser glasses I shall be leaving the garage during test fireing.

I plan on actualy making a rear mirror out of aluminum. From what I understand Al reflects ir well. I have had some success making telescope mirror of reasonable quality from scrap aluminum.

I shall post a pic or two of the rod in a moment. The yag rod is refurbished from V.j.E.
enterprises part number 86-54 I have no clue of the doping percentages. From what I understand the slight perple tint indicates a low % nd doping. Other research seems to imply low dope means cw usage...

All I realy want to get out of this project is a popped popcorn kernel or two lol maybe if I can grow a ktp crystal make a big green laser pointer... I. Once read about a guy making his own ktp crystals out of potassium triphosphate fertalizer.... who knows if I can get that down I am deffinitly not a chemist.
I have a thee foot length of solid strand fiber maybe couple laser to fiber to make that giant laser pointer easier to mannage but that is wayyyy far down the road... I just wanna get lasing first.

Sorry for the ramble

1314958324 4055 FT123366 Img 20110902 030015

1314958324 4055 FT123366 Img 20110902 030059

Daedronus

Fri Sept 02 2011, 10:46AM

Registered Member #2329 Joined: Tue Sept 01 2009, 08:25AM
Location:
Posts: 370

1. the HR is rather critical, it needs to be over 99% R, more like >99.9R, aluminum will not do that.
2. the color of the rod is not a good indication of doping %, I have 0.6% and 1.3% dopped rods, and I can't differentiate the color.
3. CW lamp pumped rods are sometimes 1.3% doped, diode pumped are usually 0.6%, but, it depends...
4. there is no way you can grow a ktp, maybe a KDP
5 yo won't pop kernels with a flash lamp nd:yag, but you will blast holes in them, if the laser is working :)

try to use as little improvised things as possible in the beginning, because the laser will most definitely not work from the first try. It can take me up to a hour to align the mirrors from a completely unaligned state, and you don't want to keep wandering if it's the AL mirror, or something else, or it is just a bad aliment.

You can also look at my videos to see a example of a nd:yag laser put together by me, working.

genoober

Fri Sept 02 2011, 10:54AM

Registered Member #4055 Joined: Tue Aug 16 2011, 06:56AM
Location:
Posts: 8

I've heard of medical lasers that use halogen bulbs to drive nd:yag here is just a nutty idea... high airflow into a pipe to cool the rod from two 250watt halogen bulbes and use photo flashes to boost pulse a cw laser??? Maybe I'm just floating bull but as I am still sourcing parts any changes I should make to my laser plan should be now before I start actualy building.

I've got a few books on laser theory... I'm going to read. The math may be above my head
(Pre-calculus back in collage a few years ago)...

Daedronus

Fri Sept 02 2011, 12:43PM

Registered Member #2329 Joined: Tue Sept 01 2009, 08:25AM
Location:
Posts: 370

The efficiency of nd:yag pumping is something like this (assuming good pump chambers and optimum OC and HR mirrors):

tungsten lamp, 0.5% electrical to optical
arc lamp 2-3% electrical to optical
flash lamp 1% or more electrical to optical, it's less then the arc lamp, because the emission spectrum is shifted to UV
808nm laser diode 30% optical to optical, the diode itself is about 50% electrical to optical.

This are just ballpark values of what to expect, and I might be completely wrong.

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